This invention relates to a crusher for concrete structures, which is adapted to crush walls, floors, foundations of concrete structures and also adapted to shear iron bars of concrete structures.
Conventional measures for demolishing concrete buildings include explosion by the use of explosives, crushing by the use of machine drills or rock borers utilizing air pressure, falling under the category of hand hammers including sinkers and jack hammers, and crushing by the use of a dropping steel ball. However, explosion by the use of explosives is only possible under limited conditions, while crushing by the use of pneumatic drills, etc. causes large noise, providing a problem of public nuisance. On the other hand, the use of a steel ball for crushing an object requires a large operating space where an associated crane lifts the steel ball up to a high level to drop same against the object through a sufficient dropping stroke to impart sufficient crushing energy to the object.
To solve these problems, a crusher has been developed and used, which comprises a support frame controllable in position by a hydraulic cylinder/link assembly, a pair of crushing claws oppositely disposed and pivotally supported on the support frame, and a hydraulic cylinder interposed between the claws at one side thereof to forcibly open and close the bladed portions of same at the other side, wherein a concrete structure to be crushed is held between the toothed portions of the claws, and the hydraulic cylinder is operated to force the toothed portions to apply pressure to the structure to thereby crush same.
However, according to this conventional crusher, if the hydraulic cylinder is operated when the nipping or toothed faces of the claws engage with the opposite side wall surfaces of a concrete structure obliquely thereto or not parallelly therewith, a torsional force is produced which acts upon the claws to bring their toothed or nipping faces into parallel contact with the opposite side wall surfaces of the concrete structure. As a consequence, the support frame and the hydraulic cylinder/link assembly also undergo this torsional force, and even can be damaged thereby.
To overcome this disadvantage, a crusher for concrete structures has been proposed by Japanese Pat. Publication No. 58-14909 issued Mar. 23, 1983, which comprises a head carried by a traveling carrier, a rotating base supported by the head concentrically therewith for rotation relative thereto, a pair of hydraulic cylinders pivotally supported at ends by the rotating base and disposed symmetrically with respect to the axis of the rotating base, a pair of jaw members as crushing claws pivotally supported by the rotating base and disposed symmetrically with respect to the axis of the rotating base, and click-stop means provided between the rotating base and the head, the hydraulic cylinders being drivingly coupled to the jaw members. According to this proposed crusher, as the hydraulic cylinders are operated, the rotating base is rotated relative to the head through suitable angles depending upon the initial angle of contact of the jaw members with an object to be crushed, so as to automatically bring the jaw members into a stable angular position where they can apply a maximum crushing load to the crushing object, thereby preventing torsional deformation or breakage of the aforementioned support frame, etc.
However, in this proposed crusher, the coupling means for rotative coupling of the rotating base to the head has rather a rigid or stiff structure comprising a central hole formed through the head, a shaft protruded from one end surface of the rotating base and rotatively penetrating the above central hole, and a retainer ring fitted around the central hole and secured thereto by bolts. It is therefore not well pliable or flexible to loads applied thereto by the hydraulic cylinders and the jaw members during operation. Besides, metal powder is produced by frictional sliding contact between the component parts of the coupling means, which impedes smooth rotation of the rotating base relative to the head. Moreover, the hydraulic cylinders and the jaw members are each pivotally supported by the rotating base by means of a single fulcrum shaft, with the result that loads are concentrated on the single fulcrum shaft to deform same, and can even cause breakage of same. Still further, the two jaw members are asymmetrical in shape with each other and accordingly their common center of gravity is not located just at the middle point between them. As a consequence, it is often difficult to bring the jaw members into biting engagement with a crushing object, especially when the jaw members are inclined with respect to the horizontal line or positioned horizontally.